What is wrong with my trans? (4L60E)

I am having a problem with my trans shifting. It is a 1995 4L60E. I had it rebuilt a few months ago. When I first got it put in it started doing this then it stopped and did fine then it started again this weekend. It will not shift from first to second until around 25 mph. Then it will not shift from second to third until around 50 mph. The only way that I have found to get it to shift into over drive is to get it up to about 80 on the interstate then set the cruise and then hit the back down button and coast down to about 70 and it will usually stay in OD for a few minuets, but it won't stay for long. The guy the rebuilt the trans is telling me it is likely a computer problem, but I have no idea. Has this ever happened to anyone else or does anyone know what is causing this?

It doesn't do it every time I get in the truck, just most of the time now. I can tell that it is going to do it when I get in and push the break and put the truck in gear, it will lurch like it is under some heavy pressure. When it doesn't do that it will drive fine.

My 95 did the same Lurch thing also, when that happened it would not shift into first gear, it would always stay in second. Then when it did shift it slammed into the next gear. It only happened if I let it idle for a long time. If I shut it off and let it sit for a minute or two and restarted it, it would run fine. I never figured out what the issue was. I did have the shift solenoids changed under warranty and it fixed it for a while.